1. Field of the Invention
The present invention generally relates to expandable endoprosthesis devices, in particular expandable intraluminal vascular grafts, generally called stents, adapted to be implanted into a body lumen, such as a coronary artery, to maintain the patency of the lumen. These devices are frequently used in the treatment of atherosclerotic stenosis in blood vessels, especially after percutaneous transluminal coronary angioplasty (PTCA) procedures, with the intent to help reduce the likelihood of restenosis of a blood vessel. Stents are also used to support a body lumen where a flap or dissection has occurred or in general where the lumen is weak. The present invention also relates to an expandable intraluminal vascular graft that can be used in any body lumen.
2. Description of Related Art
In typical percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral arteries and is advanced therein until the distal tip thereof is in the ostium of the desired coronary artery. A guidewire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced through the guiding catheter with the guidewire slidably disposed within an inner lumen of the dilatation catheter. The guidewire is first advanced out of the distal end of the guiding catheter and is maneuvered into the patient's coronary vasculature containing the lesion to be dilated, and is then advanced beyond the lesion. Thereafter, the dilatation catheter is advanced over the guidewire until the dilatation balloon is located across the lesion. Once in position across the lesion, the balloon of the dilatation catheter is filled with radiopaque liquid at relatively high pressures (e.g., greater than about 4 atmospheres) and is inflated to a predetermined size (preferably the same as the inner diameter of the artery at that location) to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall to thereby dilate the lumen of the artery. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
By way of example, further details of angioplasty and the devices used in such procedures can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert), U.S. Pat. No. 4,332,254 (Lundquist), U.S. Pat. No. 4,439,185 (Lundquist), U.S. Pat. No. 4,168,224 (Enzmann, et al.), U.S. Pat. No. 4,516,972 (Samson), U.S. Pat. No. 4,582,181 (Samson), U.S. Pat. No. 4,538,622 (Samson, et al.), U.S. Pat. No. 4,597,755 (Samson), U.S. Pat. No. 4,616,652 (Simpson), U.S. Pat. No. 4,748,982 (Horzewski, et al.), U.S. Pat. No. 4,771,778 (Mar), and U.S. Pat. No. 4,793,350 (Mar, et al.), which are hereby incorporated herein in their entirety.
A common problem that sometimes occurs after an angioplasty procedure is the appearance of restenosis at or near the site of the original stenosis in the blood vessel which requires a secondary angioplasty procedure or a bypass surgery. Another occurrence which reduces the success of an angioplasty procedure is that frequently the stenotic plaque or intima of the blood vessel or both are dissected during the angioplasty procedure by the inflation of the balloon. Upon the deflation of the balloon, a section of the dissected lining (commonly termed a "flap") will collapse into the bloodstream, thereby closing or significantly reducing the blood flow through the vessel. In these instances, surgery is sometimes required to avoid a further blockage of the artery.
Conceivably, the dilatation catheter could be replaced with a perfusion type dilatation catherter such as described in U.S. Pat. No. 4,790,315 (Mueller, Jr. et al.) in order to hold the blood vessel open for extended periods. However, perfusion type dilatation catheters have relatively large profiles which can make advancement thereof through the blockage difficult. Additionally, the inflated balloon of these perfusion catheters can block off a branch artery, thus creating ischemic conditions in the side branch distal to the blockage.
In recent years, various devices and methods (other than bypass surgery) for prevention of restenosis and repairing damaged blood vessels have become known which typically use an expandable cage or region (commonly termed "stent") on the distal end of the catheter designed to hold a detached lining against an arterial wall for extended periods to facilitate the reattachment thereof. Some stents are designed for permanent implantation inside the blood vessel and others are designed for temporary use inside the vessel. By way of example, several stent devices and methods can be found in U.S. Pat. No. 4,998,539 (Delsanti), U.S. Pat. No. 5,002,560 (Machold, et al.), U.S. Pat. No. 5,034,001 (Garrison, et al.), U.S. Pat. No. 5,133,732 (Wiktor), and U.S. Pat. No. 5,180,368 (Garrison).
Typically, the expandable region of these stents is formed by a braided wire attached to the distal end of the catheter body. Such braided designs are often difficult and expensive to manufacture, and can create reliability concerns due to the existence of high stress points located at the connection of the braided wire region with the catheter body and at the connections between the intermingled wire strands.
Alternatively, the expandable stent can be formed by a helical metal or plastic spring that is mechanically restrained in a contracted state during delivery to a predetermined position within a vessel. After placement, the mechanical restraint is released, allowing the helical spring stent to self-expand rapidly against the inner walls of the vessel. Examples of such stents are disclosed in U.S. Pat. No. 4,768,507 (Fischell, et al.), U.S. Pat. No. 4,990,155 (Wilkoff), and U.S. Pat. No. 4,553,545 (Maass, et al.).
In expandable stents that are delivered with expandable catheters, such as balloon catheters, the stents are positioned over the balloon portion of the catheter and expanded from a reduced diameter to an enlarged diameter, greater than or equal to the diameter of the artery wall, by inflating the balloon. Stents of this type can be expanded to an enlarged diameter by deforming the stent, by engagement of the stent walls with respect to one another, and by one-way engagement of the stent walls together with endothelial growth into the stent. Examples of such expandable catheters and stents are disclosed in U.S. Pat. No. 5,102,417 (Palmaz), U.S. Pat. No. 5,123,917 (Lee), and U.S. Pat. No. 5,133,732 (Wiktor) which are hereby incorporated herein in their entirety.
The disadvantage of many of the current expandable stents is that once expanded, they cannot be easily contracted and moved if they are in the wrong position within the lumen. Another problem occurs where the length of the stent shortens when expanded, and the stent is no longer large enough to cover the entire site of repair. In both cases it would be advantageous to be able to contract the stent, withdraw it from the vessel and replace it if necessary, or reposition it before final implantation.
What has been needed, and heretofore unavailable is an intravascular stent that can be placed at the site of a damaged body lumen requiring repair, evaluated, and repositioned if necessary before being locked into place. The present invention fulfills this need.